Disease relevance of picene

• Epicutaneous application of both PAHs (600 nmol/animal) followed by chronic treatment with 12-O-tetradecanoyl-phorbol-13-acetate for 24 weeks led to the formation of papillomas in 93% of animals treated with DBA while picene showed no tumorigenic activity at all [1].
• When newborn mice were s.c. treated once on day 2 of their life with each of the two PAHs (400 nmol/animal), 27.8% of treated animals developed lung adenomas after 40 weeks in the case of picene compared to 92.1% in the case of DBA [1].
• Single s.c. treatment of adult mice with picene or DBA (308 nmol/animal, each) led to the formation of fibrosarcomas in 63.3% of treated animals regardless of the PAH used [1].
• Similar treatment with picene did not induce sarcoma in any test animals by 37 weeks (0%) [2].

High impact information on picene

• This rare biological property of picene, which is a complete carcinogen, yet at most a very weak tumor initiator, is explained in terms of its inefficient biotransformation to mutagenic and carcinogenic metabolites as compared to the strong tumor initiator DBA [1].
• 5. Cell lines were validated in mutagenicity, cytotoxicity, and metabolism studies employing benzo[a]pyrene, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene, cyclophosphamide, ifosfamide, and picene [3].
• In order to find out if the metabolism of this PAH can provide an explanation for its lack of carcinogenicity, picene was incubated with the hepatic microsomal fraction of Sprague-Dawley rats, which had been pretreated with Aroclor 1254 [4].
• The lacking carcinogenicity of picene could therefore result from the inability of microsomal enzymes to transform its M-region dihydrodiol to dihydrodiol bay-region epoxides in amounts necessary to initiate carcinogenesis [4].

Analytical, diagnostic and therapeutic context of picene

• Early carcinogenicity tests found no evidence of activity for picene but found considerable initiating and carcinogenic activity for dibenz[a,h]anthracene (DBA) [2].

References